1. Field of the Invention
The invention proceeds from a membrane pump in accordance with the preamble of the main claim.
2. Discussion of the Prior Art
From German Utility Model G 94 06 216 there is known a membrane pump in accordance with the preamble of claim 1. The membrane pump of this utility model has a membrane which can be actuated by crank drive, which membrane is attached at an outer membrane circle ring to a pump body of a pump housing. Along with the outer membrane circle ring, the membrane has a membrane core which is connected with the outer membrane circle ring via an elastically deformable membrane ring. The membrane, with a pump body surface formed on the pump body, bounds a pump chamber (compression/expansion chamber). An inlet channel and an outlet channel are formed in the pump body, which open out at an inlet opening and an outlet opening in the pump body surface. The inlet channel and the outlet channel are, outside the pump body, preferably connected with directional valves, by means of which one direction of flow is predetermined through the inlet channel and the outlet channel. Upon a suction stroke of the crank drive, a pump medium is transported through the inlet channel into the pump chamber and upon a following expulsion stroke of the crank drive the pump medium is displaced out of the pump chamber via the outlet channel.
Disadvantageous with the membrane pump known from German Utility Model G 94 06 216 is that during the expulsion stroke a part of the pump medium located in the pump chamber is pressured back or compressed into the inlet channel. In particular in the case of a compressible pressure medium, for this reason the efficiency of the membrane pump significantly worsened. A further disadvantage is that the outlet opening is choked in dependence upon the stroke position of the crank drive, the choking increasing before attainment of the top dead center position of the crank drive, so that at the end of the expulsion stroke the highly compressed pump medium can increasingly poorly escape.
Summarizing, with the known membrane pump a quantity of pump medium corresponding to the compression ratio of the membrane pump cannot be completely expelled out of the pump chamber via the outlet opening. Further, the known membrane pump is suitable only to a limited degree for compressible pump mediums such as for example gases.
The object of the present invention is to propose a membrane pump which avoids the disadvantages of the state of the art and allows a compression ratio of the pump medium located in the pump chamber which is as great as possible.
The object is achieved by means of the membrane pump in accordance with the invention having the characterizing features of the main claim. Advantageous developments of the invention are indicated in the subclaims.
The membrane pump in accordance with the invention has the advantage that the inlet opening of the inlet channel is already closed during the explosion stroke of the crank drive, so that a further compression of a pump medium takes place only in the pump chamber and the pump medium can be expelled completely via the outlet channel.
It is advantageous when the middle point of the inlet opening lies at least approximately in the plane of rotation of the crank of the crank drive. By these means, the inlet opening of the inlet channel is closed at a particularly early time point.
It is advantageous when a surrounding control edge is formed in the edge region of the inlet opening, on which control edge the elastically deformable membrane ring closes the inlet opening. By these means the inlet opening is reliably closed on all sides.
In an advantageous manner, the elastically deformable membrane ring closes the inlet opening with a crank rotary position of the crank drive which is up to 90xc2x0 before top dead center. By these means, from a maximum deflection of the membrane of the membrane pump, sealing off is attained.
In advantageous manner, the elastically deformable membrane ring closes the inlet opening at a crank rotary position of the crank drive which lies 20xc2x0 to 90xc2x0 before top dead center. By these means a sealing of the inlet opening of the inlet channel is attained from a maximum deflection of the membrane of the membrane pump, whereby with a closed inlet opening of the inlet channel a part of the crank rotation is available in order to attain a greater compression of the pump medium.
It is of advantage when a valve plate is arranged in a region of the inlet opening of the inlet channel for forming a directional valve. In that the valve plate is arranged directly at the inlet opening of the inlet channel, the dead volume of the inlet channel can be further reduced. Thereby it is particularly advantageous when the middle axis of the inlet channel is orientated perpendicularly to the pump body surface. By these means the structural configuration of the directional valve and the emplacement of the valve plate in the inlet channel is simplified.
In an advantageous manner, the outlet opening of the outlet channel is arranged in a region of the pump body surface which the membrane last approaches and which is attained by the membrane at the earliest with the top dead center position of the crank drive. Thereby it is achieved that the pump medium can be pumped out of the pump chamber into the outlet channel as far as possible unchoked. Further, it is achieved that the outlet opening of the outlet channel is not already closed before the attainment of the top dead center position of the crank drive.
It is of advantage when the middle point of the outlet opening of the outlet channel is arranged in an inner region of the pump body surface which lies opposite to a membrane core of the membrane. Since upon the crank movement of the crank drive, the pump medium is pumped last out of the region the pump chamber arranged above the membrane core of the membrane, as a result of the movement of the membrane core, the outlet opening of the outlet channel is thereby particularly favourably arranged.